In a vehicle (electric vehicle) such as an electric vehicle using only an electric motor as a power source, and a hybrid vehicle using an engine (internal combustion engine) and an electric motor as power sources, which includes the electric motor serving as the power source, there is a vehicle arranged to simulate a creep torque generated by a torque converter of an automatic transmission in a vehicle using the engine as the driving source, to control a minute torque corresponding to the creep torque by the electric motor, to output this as the creep torque, and thereby to perform the creep traveling of the vehicle.
Moreover, in the electric vehicle which can perform the creep traveling, there is developed an art to cut the creep torque to suppress electricity consumption at the brake operation.
For example, a patent document 1 discloses an electric vehicle including a motor control section configured to generate the creep torque when a creep torque condition in which a selected shift range is a traveling range and an accelerator pedal is not operated is satisfied, and to perform a creep torque cut control to cut the creep torque when a creep cut condition in which the vehicle is stopped and the foot brake is operated is satisfied even when the creep torque condition is satisfied.
It can be judged whether or not the foot brake is operated, from information from a brake sensor arranged to sense whether or not the foot brake is operated. This brake sensor includes a stroke sensor arranged to sense a depression stroke amount of the brake pedal. It is possible to surely sense whether or not the foot brake is operated, by sensing a sensor stroke value (0 point, brake joint point) at which the brake hydraulic pressure is started to be increased by the depression of the brake pedal, and to apply (act) the brake.
This 0 point is varied in accordance with the variation of the brake with time, maintenance, and so on. Accordingly, this 0 point is periodically updated (renewed) by a stroke learning. It is possible to perform this stroke learning by reading a detection value of the stroke sensor at which the brake hydraulic pressure is started to be increased by actual operation of the foot brake.
In this case, there is developed an art to perform the stroke learning from a relational information of the brake hydraulic pressure and the detection value of the stroke sensor which is obtained by the operation of the foot brake along the ON state→the OFF state when the foot brake is operated along the ON state→the OFF state→the ON state after the start operation of the vehicle (the ON operation of the key switch).
By the way, in a case where the stroke learning of the brake sensor (the stroke sensor) is performed when the foot brake is operated along the ON state→the OFF state→the ON state after the start operation of the vehicle (the ON operation of the key switch) as described above, the detection signal of the brake sensor (the brake signal) is made invalid until the stroke learning is finished. With this, various controls are performed by using only the brake sensor information to which the result of the stroke learning is reflected. Accordingly, it is possible to appropriately perform the various controls.
However, in the vehicle in which the creep torque is generated at the satisfaction of the creep torque generation condition, and in which the creep torque is cut at the satisfaction of the creep cut condition as described above, the forward and rearward G variation is generated in the vehicle in a specific state, by using the only brake sensor information to which the result of the stroke learning is reflected. Consequently, the unnatural feeling is provided to the driver.
For analyzing the above-described phenomenon, for example, it is supposed that the key switch of the vehicle is operated to the ON state in the depression state of the brake pedal, and that the shift lever is operated to slowly switch the shift range from the P range through the R range to the N range. In this case, the foot brake is held to the ON state (depression state) after the start operation of the vehicle. Accordingly, the stroke learning is not performed. The brake signal is in the invalid state. The motor control section judges that the foot brake is not operated.
In this state, when the shift range is switched from the P range to the R range, the creep torque generation condition in which the shift range is the traveling range and the accelerator pedal is not operated is satisfied in the R range. The creep cut condition in which the vehicle is stopped and the foot brake is operated is not satisfied. Accordingly, the electric motor generates the creep torque.
In this R range, the distortion by the creep torque is stored in the drive shaft and so on of the vehicle. Then, when the shift range is switched to the N range, the creep torque of the electric motor is released, and the clutch engagement of the transmission is released. With these, the creep torque stored in the drive shaft and so on is suddenly released, so that the forward and rearward G variation is generated to the vehicle.